Showing papers on "Double bond published in 1976"

Water absorbing starch resins

Abstract: A highly water-absorbent resin is produced by polymerizing (A) starch or cellulose, (B) at least one monomer having a polymerizable double bond which is water-soluble or becomes water-soluble by hydrolysis and (C) a crosslinking agent, and subjecting, if necessary, the resulting product to hydrolysis.

Catalyzed Addition of Aldehydes to Activated Double Bonds—A New Synthetic Approach

Abstract: In the presence of cyanide ions as catalyst, aromatic and heterocyclic aldehydes can be smoothly added to α,β-unsaturated ketones, esters, and nitriles in aprotic solvents to form γ-diketones, 4-oxo carboxylic esters, and 4-oxo nitriles. Thiazolium salts in the presence of bases are also suitable catalysts; they permit not only addition of aromatic and heterocyclic aldehydes but also the addition of aliphatic aldehydes.

Subvalent Group 4B metal alkyls and amides. Part I. The synthesis and physical properties of kinetically stable bis[bis(trimethysilyl)methyl]-germanium(II), -tin(II), and -lead(II)

Abstract: Two methods are described for the synthesis of the unusual bivalent Group 4B metal alkyls M[CH(SiMe3)2]2(M = Ge, Sn,or Pb)from Li[CH(SiMe3)2] indiethyl ether at 0 to –20°C and (a) the metal(II) chloride (M = Sn or Pb) or (b) M[N(SiMe3)2]2(M = Ge or Sn). At ambient temperature in cyclohexane or benzene the solutions are yellow (Ge), red (Sn), or purple (Pb), and the compounds are monomeric and in a singlet electronic ground state. There are colour changes between the solid and the melt, and the compounds tend to become colourless at –196 °C. The crystal structure of the tin(II) alkyl shows a centrosymmetric dimer with a Sn–Sn bond (2.76 A) similar in length to that in Sn2Ph6, and the two pairs of geminal alkyl groups in a mutually trans arrangement. The solid germanium compound is inferred to be structurally similar because of the presence of a strong polarised Raman line at 300 cm–1. The monomer is believed to be angular with three approximately sp2 hybridised orbitals at the metal, one of which is non-bonding; the dimer. with a SnSn bent double bond, is formed by overlap of the non-bonding orbital of each monomer unit with the orthogonal vacant pz orbital of the other.

Application of self-consistent-field ab initio calculations to organic molecules

Abstract: Self-consistent-field ab initio calculations of the equilibrium geometries, r calc e, and quadratic force constants for methane, ethane, propane, ethene, cyclopropane and cyclopropene have been carried out using an extended basis of contracted gaussian functions (4–31G). In the case of unstrained saturated molecules or parts of molecules a simple (anharmonicity) correction yields calculated structures for which the average deviation with ‘best’ experimental bond lengths and angles is 0·003 A and 0·4° respectively. Calculated carbon-carbon double bonds are typically too short by a constant amount (0·022 A). The average deviation of calculated and experimental bond angles about CH2 groups in three membered rings and those about sp2 hybridized carbons are 1·5° and 1·0° respectively. Quadratic force constants for symmetric stretchings are compared with force constants deduced from vibrational analysis. Trends and differences are discussed.

On the Way to Carbene and Carbyne Complexes

Abstract: Publisher Summary The chapter focuses on carbene andcarbyne complexes. If one of the hydrogen atoms in an alkane hydrocarbon, such as ethane, is formally replaced by a metal atom, an organometallic compound in which the organic entity is bonded to the metal by a σ-bond is obtained. If a system with 2 carbon atoms bonded to each other by a double bond, i.e., an alkene molecule, is considered, a number of separate paths leading to organometallic derivatives are recognized. One path involves the replacement of a substituent by a metal atom and leads to σ compounds that are exemplified by vinyl-lithium derivatives. If molecules with a carbon-carbon triple bond of the type that exists in alkynes are considered, then it is realized that there also are three possible paths to metal-containing derivatives. The chapter discusses various properties of transition metal-carbene complexes such as preparation of the first carbene complexes, bonding concepts, and spectroscopic findings. It also presents various properties of transition metal-carbyne complexes such as preparation of the first carbyne complexes and x-ray structural analyses.

Synthese von optisch aktiven, natürlichen Carotinoiden und strukturell verwandten Naturprodukten. I. Synthese der chiralen Schlüsselverbindung (4R, 6R)‐4‐Hydroxy‐2,2,6‐trimethylcyclohexanon

Abstract: Synthesis of optically active natural carotenoids and structurally related compounds. I. Synthesis of the chiral key compound (4R, 6R)-4-hydroxy-2,2,6-trimethylcyclohexanone. A technical synthesis of (4R, 6R)-4-hydroxy-2,2,6-trimethylcyclohexanone (7) starting from the readily available oxo-isophorone (2) is described. 7 is an ideal precursor for the synthesis of naturally occurring, optically active hydroxylated carotenoids (e.g. zeaxanthin, cryptoxanthin and structurally related compounds). Chirality is introduced at C(6) by a stereoselective fermentative hydrogenation of the double bond using baker's yeast as the biocatalyst. Thereafter the carbonyl group at C(4) is reduced selectively and stereospecifically by chemical methods to the corresponding alcohol. Chemical reduction is preferably carried out by hydrogenation in the presence of a nickel catalyst or using triisobutylaluminium as the reducing agent. Stability, stereochemistry and physical properties of 7 and the stereoisomers thereof are discussed.

Carotenoid-Protein Complexes

Abstract: A survey of carotenoid-protein complexes is presented. Distinction is made between astaxanthin-proteins in which the absorption band of the carotenoid is unaltered in shape, and carotenoid-lipoglycoprotein complexes. The proposal by Buchwald and Jencks 79 that the carotenoid is twisted about the double bonds of the polyene chain, is discussed and sustained for astaxanthin-proteins. A mode of binding for the carotenoid in these complexes is proposed, involving hydrogen-bonding of keto groups of the polyene to imide groups of peptide bonds of the apoprotein.

Metabolism of alkenebenzene derivatives in the rat. II. Eugenol and isoeugenol methyl ethers.

Abstract: 1. The metabolites of 3,4-dimethoxyallylbenzene (eugenol methyl ether) and 3,4-dimethoxypropenylbenzene (isoeugenol methyl ether) in the rat were identified and quantitatively determined by g.l.c. and g.l.c—mass spectrometry.2. The major metabolic reactions of 3,4-dimethoxyallylbenzene were oxidation of the allylic side chain to 2-hydroxy-3-(3,4-dimethoxyphenyl)-propionic acid, 3,4-dimethoxybenzoic acid and 3,4-dimethoxycinnamic acid, the two latter being largely excreted as their glycine conjugates. The formation of the hydroxy acid presumably involved epoxidation of the double bond and subsequent hydration to the diol whereas the formation of 3,4-dimethoxycinnamic acid and 3,4-dimethoxybenzoic acid involved migration of the double bond and the formation of cinnamoyl intermediates. Other reactions were O-demethylation to 4-hydroxy-3-methoxyallylbenzene (eugenol) and 3-hydroxy-4-methoxyallylbenzene in equal amounts, oxidation to l-(3,4-dimethoxyphenyl)-2-propen-l-ol, hydroxylation of the benzene ring to a...

Elimination Reactions over Polar Catalysts: Mechanistic Considerations

Abstract: In order to form a double bond in an organic molecule, two fragments (atoms or groups) are abstracted from adjacent carbon atoms. Such a reaction is called a β-elimination [12, 221. In many cases one of the fragments is hydrogen.

Carbon-13 NMR Spectra of Carotenoids

Abstract: The 13C-NMR spectrum of β-carotene has been assigned using data from deuterium labelled samples, and cis vitamin A. A study of methyl β-apo carotenoates is consistant with this result. Spectra of derivatives of β-carotene, such as zeaxanthin, isozeaxanthin, violaxanthin and alloxanthin, have been analysed. The stereochemistry of lutein is deduced from its spectrum to be trans between the 3′-hydroxyl group and the polyene chain at C-6′. It is suggested that isomytiloxanthin has the alkyl groups at C-5 and C-6 of the cyclohexanone ring trans. Cis double bonds give characteristic changes in the spectrum compared with that of the corresponding trans compound violeoxanthin is shown to be the 9-cis isomer of violaxanthin. 13C-31P coupling over six bonds is observed with trans β-C15 Wittig salt, but only over four bonds with the cis isomer. The 15,15′-cis-β-carotene spectrum suggests a revision of the assignment of the phytoene spectrum. Using the data from appropriate apo esters and other model compounds the spectra of capsorubin and azafrin are analysed. The absence of suitable model compounds as yet prevents a complete assignment of the fucoxanthin spectrum.

The use of ion‐molecule reactions in the mass spectrometric location of double bonds

Abstract: A method for the location of the positions of carbon-carbon double bonds using high pressure mass spectrometry is proposed. A known olefinic molecular ion reacts with a second, unknown olefin to form a four-centre complex, which fragments with retention of the structural identity of methylene and substituted methylene groups to eliminate a new olefin molecule and to form an unsaturated ion from which the position of the double bond in the unknown olefin can be inferred. Vinyl methyl ether proved to be a convenient reagent gas and its molecular ion undergoes the required reaction with several classes of olefinic compound. Conjugated dienes and unsaturated compounds containing electronegative groups do not undergo this reaction.

13C nuclear magnetic resonance spectroscopy of saturated, unsaturated, and oxygenated fatty acid methyl esters

Abstract: Chemical shifts have been assigned to all the separate signals in the13C nuclear magnetic resonance spectra of methyl stearate, oleate, and petroselinate by means of the second and third atom isotope effects in spectra of specifically deuterated esters. Spectra of almost all the isomeric hydroxy, acetoxy, and oxo stearates were also measured. From the assignments, the effects of the introduction of a double bond or an oxo, hydroxy, or acetoxy group at different positions on the fatty acid chain on the13C nuclear magnetic resonance spectra were determined. All the isomeric oxo stearates and most of the hydroxy and acetoxy stearates can be distinguished and identified by their13C spectra.

Quantitative aspects of the photochemistry of isomeric retinals and visual pigments.

Abstract: The photoisomerization quantum efficiencies of all-trans-, 9-cis-, 1 1-cis-, 13-cis-, and 9-cis, 13-cis-retinal were determined upon direct excitation in polar and nonpolar solvents and biacetyl triplet sensitization in a polar solvent. The four cisretinals had quantum yields of 20% in nonpolar solvents and 4-5% in polar solvents. The biacetyl triplet sensitized quantum yields of the cis isomers were also ca. 20%. while all-trans-retinal underwent no detectable triplet isomerization. High-pressure liquid chromatography was used to analyze the photoproducts. It was found that only two types of carbon double bonds isomerized, the cis bonds and the terminal carbon double bond. Photobleaching of rhodopsin, isorhodopsin, and 9.1 3-isorhodopsin (isorhodopsin 11) gave stereospecifically all-trans-retinal. When rhodopsin was treated with the unique triplet sensitizer, trimethyl1,2-dioxetane, the protein was denatured and the chromophore isomerized. Based on product studies and quantum yield measurements, it is concluded that in the cis-retinals the photoisomerization occurred from the singlet and triplet states. In visual pigments it is not possible to assign the state from which isomerization occurred.

Light-sensitive composition

Abstract: A light-sensitive composition comprising of 1. an N-nitroso compound having the general formula ##STR1## wherein R 1 and R 2 , which may be the same or different, are each a member selected from the group consisting of a monovalent hydrocarbon radical, a monovalent hydrocarbon radical attached to the nitrogen atom of amine through --SO 2 --, and a group of the formula ##STR2## where X is a divalent hydrocarbon radical, and R 3 is a monovalent hydrocarbon radical, which may be the same as R 1 or different therefrom, which R 1 , R 2 and R 3 may have substituent groups, and R 1 and R 2 may together form, directly or by being bonded through an oxygen atom or nitrogen atom, a ring; 2. a photopolymerization initiator; and 3. a compound having a photopolymerizable ethylenic double bond in its molecule.

Method of inducing an estrogenic response

Abstract: Compounds of the following general formula are useful in inducing an estrogenic response in a patient in need thereof: ##STR1## wherein R is --CHO or --CH 2 OR 1 ; each of R 1 and R 2 is hydrogen, alkylcarbonyl wherein the alkyl moiety has from 1 to 20 carbon atoms and is straight or branched, benzoyl, phenylalkylcarbonyl wherein the alkyl moiety has from 1 to 6 carbon atoms and is straight or branched or cycloalkylcarbonyl wherein the cycloalkyl moiety has from 5 to 10 carbon atoms; R 3 is hydrogen; or R 2 and R 3 together form a double bond between the 17-position carbon atom and the oxygen atom.

Synthesis of monomers that expand on polymerization. Synthesis and polymerization of 3,9‐dimethylene‐1,5,7,11‐tetraoxaspiro[5.5]undecane

Abstract: A spiro ortho-carbonate containing two double bonds, 3,9-dimethylene-1,5,7,11-tetraoxaspiro[5.5]undecane (III) was prepared from 2-methylene-1,3-propanediol (VI). The structure of the monomer was indicated by its elementary analysis as well as its infrared and NMR spectra. When the crystalline monomer was polymerized with Lewis acids such as trifluoride etherate as catalysts, soluble polymer with a high molecular weight was obtained. The infrared and NMR spectra indicated that the polymer was an alternating copolymer of ether and carbonate having double bonds. When the usual monomers such as vinyl chloride and styrene polymerize, shrinkage occurs. However, this monomer underwent expansion on polymerization.

A stereospecific synthesis of vitamin A from 2,2,6-trimethyl-cyclohexanone.

Abstract: An efficient synthesis of all-(E) vitamin A acetate from 2,2,6-trimethyl-cyclohexanone has been achieved via the intermediacy of 1-(9-acetoxy-3, 7-dimethyl-nona-3,5,7-trien-1-ynyl)-2,2,6-trimethyl-cyclohexanol (25), readily prepared in high yield by allylic rearrangement of tertiary propenols with glacial acetic acid. The key step in the synthesis is the transformation of 25 to the unsaturated ketone 27 (9-acetoxy-3,7-dimethyl-1-(2,6,6-trimethyl-cyclohex-1-enyl)-nona-3,5,7-trien- 2-one) using a novel vanadium(V)-catalysed rearrangement reaction. The carbonyl in 27 affords the means for the essential isomerization of the adjacent double bond to the (E) isomer and the product is readily transformed into the polyene by reduction and elimination. An overall yield of 18–31% of vitamin A acetate from 2,2,6-trimethyl-cyclohexanone has been realized.